(Throughout all my post, I will refer to “gravitational potential energy” just as “potential energy”)
Hi! I have this confusion about when is potential energy positive/negative and how it is related to how we define our axes. I think it is easier to understand my confusion with the following...
I drew a diagram for the a) part
The person is h meters high
So GPE= 100 x 9.8x h
GPE= 980h j
KE = 980h when the person hits the see saw
KE=1/2mv²
980h=0.5 x 5 x v²
Now it v²=u²+2as
For the brick going up to 10m
v = 0
u=?
a=-9.8ms-²
s=10m
u²=2 x 9.8 x 10
u=14m/s
We can assume that u=14m/s is...
Elastic Potential Energy of a Strained Body
(A) Using ## Y = \frac {stress}{strain}## we get ##F = \frac {AY}{L} * x## where ##F## is the restoring force, ##x## is the distance the body is stretched by.
Since Work = PE (spring force/ stress is conservative?)
Thus ##W = \int_{0}^{x} \frac...
A while back I thought of an issue with parallel charged plates. Imagine this: a set of opposite charged resistive plates with holes in the center. In theory, there is a finite amount of energy required to push a positive charged particle through the hole in the positive plate (in theory it...
1. Homework Statement
The system is released from rest with no slack in the cable and with the spring stretched 225 mm. Determine the distance s traveled by the 3.2-kg cart before it comes to rest (a) if m approaches zero and (b) if m = 2.5 kg. Assume no mechanical interference and no friction...
When I first learned about these subjects, I did what was intuitive to me and treated particles as if they carried potential energy. I would do this similarly for rigid bodies where I would also treat them as a particles with their body's mass at the center of mass. This wasn't helped by...
Hello everyone,
Any object has a gravitational potential energy as a function of the distance from the earth (R). Does this energy depend only on the rest mass of the object; or one must take into account it's relativistic mass?
In other words, if we imagine two identical bullets on the top...
In quantum mechanics, there exist some systems where the potential energy of some particle is a Dirac delta function of position: ##V(x) = A\delta (x-x_0 )##, where ##A## is a constant with proper dimensions.
Is there any classical mechanics application of this? It would seem that if I...
Hi All,
The Potential Energy for two chemically bonding atoms is defined by ,U=1/2(k*q1*q2)/r
So it means that when the atoms approach each other then, their Potential Energy will increase.
Where am I doing wrong?
I will be thankful for help!
What is a conservative force and how do you determine the work done by it.
It is an interesting relation between the work done by such a force and the potential energy and kinetic energy of a particle.
1. Homework Statement
A rocket burns out at an altitude h above the Earth's surface. Its speed v0 at burnout exceeds the escape speed vesc appropriate to the burnout altitude. Show that the speed v of the rocket very far from the Earth is given by v=(v02-v2esc)1/2
2. Homework Equations...
Consider the classical scenario a stone falling in the Earth gravitational field.
Classically we attach a Potential Energy to the stone and using the law of conservation of (mechanical) energy we are able to evaluate the dynamic of the falling stone.
This model assume a stone in a "external"...
1. Homework Statement
Please look at the problem attached as a screenshot.
2. Homework Equations
Assuming frictionless, Ei = Ef, which means objects that are the same will end up in the same heights (so we can group A&C, B&D, and E&F).
For A&C and E&F, mgh = KE_rot + KE_trans
For B&D, it...
1. Homework Statement
Please look at the attached screenshot.
2. Homework Equations
Assuming the ramp is frictionless, Ei = Ef and thus mgh = KE ( = 1/2mv^2, which isn't really necessary here)
3. The Attempt at a Solution
I'm okay with all other examples except for A and C. From the...
1. Homework Statement
Please look at the attached screenshot.
This problem is really confusing for me and I can't seem to make much sense out of it.
2. Homework Equations
Ei = Ef
3. The Attempt at a Solution
As you can see, I did get (a). (The other checkmarks, I guessed — there were...
Let, we want to calculate the P.E(potential energy) of a system containing 3particles p1,p2,p3.the point of observation is P.so now we should add up the P.E at P due to p1,p2,p3 to get the net potential energy of the system,but why we take the P.E of particles due to each other into count...
1. Homework Statement
Movers must push a piano onto a truck, the bed of which is a height 1.35 m above the ground. To do this they will use a frictionless ramp. If the piano has a mass of 1806.0 kg and the movers push it up the slope at a constant velocity, how much work do they need to do on...
I have been doing pendulum problems lately, and I have found 2 different formulations for potential energy of a pendulum.
U=mgl(1-cos(Θ)) and U=-mglcos(Θ)
The first says U=0 when Θ=0 (at the bottom). The second has U=0 when Θ=π/2 (halfway to the top).
Both give the same equation of motion...
1. Homework Statement
If we lift a block with constant velocity, by applying a force mg upwards, is the work done zero?
2. Homework Equations
3. The Attempt at a Solution
The work done must be zero as the resultant force is zero, what I don't understand is how does the block get potential...
Do electromagnetic waves have potential and kinetic energy like springs, strings, etc. If so how are they calculated, inter-related? What is the total energy? Are the energies fluctuating over time?
I am a physics hobbyist so generally the first answers should come with the least mathematics...
Anyone know if the following statement is true (and why)?
"Getting to higher ground would increase his gravitational potential energy, decreasing the effects of non-conservative forces, which would allow him to move easier."
CLARIFICATION: "move easier" refers to a lack of friction and not the...
I am aware that the negative derivative of potential energy is equal to force. Why is the max force found when the negative derivative of potential energy is equal to zero?
Generally, a change in altitude within a gravitational field is said to increase or decrease PE. I posit that the change in PE never occurs UNTIL there is a change in KE. Thus, in the case of an object with a constant velocity UP, there is no gain in PE until the instant that the thrust no...
1. Homework Statement
A planet is in an elliptical orbit around a star. Which of the following best represents the mechanical energy E_planet of just the planet and the mechanical energy Es_tar-planet of the star-planet system as functions of time for one complete orbit?
2. Homework...
Hi,
I know that in an elecric field the potential energy ##E_{pot}## is equal to the potential ##V## times the charge ##E_{pot}=q V##.
Here my problem:
I know that the potential energy of a spring is ##E_{pot}= \frac{1}{2}kx^2##.
In my theoretical physics book i read also that the potential is...
1. Homework Statement
Charged sphere with a mass of 15 mg and charge 2 nC moves with a speed of 15 cm/s towards a fixed point charge of 3 nC. How close will sphere approach charge?
2. Homework Equations
K=(1/2)*mv2
U=k*(Q1Q2/r)
3. The Attempt at a Solution
So I am not sure I approached...
1. Homework Statement
Hi I'm attempting to derive the gravitational potential energy of a point mass (##m##) that's moving from infinity to a point r' inside a gravitational field produced by a another mass ##M##. For simplicity I treated it as a one dimensional case. The problem I get is that...